The Premier League champions announced the £37.1million signing of the Spanish playmaker on Saturday evening.

It is a deal which it is hoped might give United's difficult campaign some impetus, with the team seventh in the league and out of both domestic cup competitions.

Talks are under way with striker Wayne Rooney to extend his agreement with the club, while there have also been reports of a bid for highly-rated Southampton left-back Luke Shaw as Moyes looks to put his stamp on the squad he inherited from Alex Ferguson.

"We see this as the start, we have to look to improve" - David Moyes

Moyes said of signing Mata: "This is the first, and there will be many more to come in time. I want the quality of Juan to be the start of it.

"I don't think we will have any more [new signings] in January - I'm still working on it and looking to do so. But hopefully it will be the first of some new signings, some new players who will arrive, more likely in the summertime."

Moyes admitted the signing had lifted the mood at Old Trafford.

"Undoubtedly we could all do with a bit of a lift, we have not done as well as we would have liked to do,” Moyes told MUTV. “We see this as the start, we have to look to improve and I'm going to try to bring in some new players to make that happen.

"I want to build an exciting team, I want to win and I want to give the supporters something to shout about - I've not done that often enough."

Moyes, who said he would probably look to get Mata involved in Tuesday night's Premier League game against Cardiff, said it was a surprise that the deal was able to be done mid-season.

"I never felt that we would get that opportunity, I wasn't sure that Chelsea would ever sell him to us. Thankfully we got there and I am delighted he is here.

"I'm a bit surprised because it's not something that tends to happen especially between Premier League teams. I was surprised when it happened but we have got a really exciting player, a player I'm looking forward to working with, a player I think everybody in football looked at and says he did a great job for Chelsea.

"I'm looking forward to seeing him in a red jersey and doing it for us."